Oil prices, which were flat earlier in the day, started rising at about the same time as stocks on the S&P 500 Index at around 10:15 a.m., two energy traders said, noting the stock index turned positive near 11 a.m.

Analysts also said prices were being propped up by "bullish comments" from oil ministers from the Organization of the Petroleum Exporting Countries and other global oil players at the CERAWeek conference in Houston, the largest energy industry conference, on Monday.

Ecuador's oil minister Carlos Perez said Venezuela's oil production is running 1.5 million barrels per day (bpd) short of its historic output. Speaking on the sidelines of the CERAWeek conference, he noted it was something that the country must address itself.

OPEC Secretary General Mohammad Barkindo and other OPEC officials are expected to hold a dinner on Monday with U.S. shale firms on the sidelines of the conference.

Suhail Mohamed Al Mazrouei, the United Arab Emirates oil minister and OPEC's current president, said on Sunday that the cartel had not discussed rolling over production cuts next year.

"We feel there is still market overhang," Al Mazrouei said, adding "there are no talks about (extending cuts into 2019) at this stage."

OPEC and other major producers agreed last year to cut combined output by about 1.8 million barrels per day to drain a global oil glut. The agreement began in January 2017 and runs through the end of this year.

Also on Monday, the International Energy Agency, which advises industrialized nations on energy policies, said it expects oil demand growth to average a fairly robust 1.1 percent a year to 2023 and noted that OPEC would fail to significantly increase its production capacity.

"One thing hasn't changed over the past year ... Upstream investment shows little sign of recovering from its plunge in 2015-2016, which raises concerns about whether adequate supply will be available to offset natural field declines and meet robust demand growth after 2020," IEA said.